If you can spot the subject and verb disagreement in the above title, you get the idea. Chances are that you are using a word processor that will check your grammar for you. And there is an equal if not better chance that you have turned off the grammar checking capability. Turn it back on. And then run a grammar check on your writing. I is appalled at how many people doesn't check their grammar. That's a joke -- get it?
Since there's so much that can be written about correct grammar, I'd rather leave the initial bit up to your comments and we'll move forward on this point from there.